1. Field of the Invention
The present invention generally relates to the field of storage devices. The present invention specifically relates to optimizing dynamic reconfiguration-switching of motor windings between one of a multiplicity of winding-configurations by selectively lowering resistance of a constantly used portion of a disk drive.
2. Description of the Related Art
In recent years, advances in technology have led to substantial changes in the design of storage devices having revolving media, for example, disk drives, tape drive, hard disk drives (HDD), and the like. For example, magnetic tape provides a means for physically storing data. As an archival medium, tape often comprises the only copy of the data. Tape may be used to restore data lost in a disk-drive crash. A tape drive is used to store and retrieve data with respect to the magnetic tape. An example of a tape drive is the IBM TotalStorage Enterprise Tape Drive 3592 manufactured by IBM Corporation. Storage devices, such as disk drives, tape drive, hard disk drives (HDD), and the like are typically used in combination with a data storage library. For example, the IBM TotalStorage Enterprise Tape Library 3494 manufactured by IBM Corporation is an automated data storage library that may include one or more tape drives and data storage media for storing data with respect to the tape drives.
Disk drive, hard disk drives (HDD), and/or tape drives frequently employ DC motors and feedback control systems with motor drivers for operating the DC motors, to produce well-controlled motion parameters such as position, velocity, and/or tape tension. While the motors rotate, a back electromotive force (“BEMF”) is produced by the disk drive, hard disk drives (HDD), and/or tape drive electric motors. This BEMF voltage is produced because the electric motors generate an opposing voltage while rotating. For example, in tape drives such as the aforementioned IBM 3592 used in the Enterprise range, and the Linear Tape Open used in the mid-range, the current tape linear velocity is limited by the tape reel's angular-velocity. The tape reel's angular-velocity approaches a maximum when the BEMF produced by the reel motor approaches the voltage of the power supply to the reel motors. Tape drives typically operate from +5 and +12 V power supplies; therefore it is not possible to increase the power supply voltage to increase the tape reel angular-velocity. In light of the foregoing, a need exists for a mechanism by which angular-velocity may be increased in disk drives, tape drives, hard disk drives (HDD), and the like incorporating fixed-voltage power supplies.